Method for agglomerating dispersed rubber

ABSTRACT

A process for the agglomeration of at least one rubber (A), dispersed in an aqueous phase, by the addition of a dispersion of at least one agglomerating polymer (B) in aqueous phase, in which the agglomerating polymer B used is one containing substantially no free acid groups and the agglomeration is carried out in the presence of at least one basic electrolyte.

[0001] The invention relates to a process for the agglomeration of atleast one rubber (A), dispersed in an aqueous phase, by the addition ofan aqueous dispersion of at least one agglomerating polymer (B).

[0002] Methods of enlarging rubber particles are known to the personskilled in the art. One variant comprises agglomeration effected duringpolymerization of the rubber-forming monomers. Another method comprisesthe agglomeration of the substantially fully polymerized dispersedrubber. In the latter process there is also the problem that thedispersion, in addition to the desired agglomeration, forms coagulum(unstable, being over-large agglomerate). The coagulum impairs themechanical properties of the end product. Furthermore, coagulationreduces the yield of product. High yields are particularly important,especially in the case of plants operated on a large scale. In addition,when coagulum forms, the plant must be cleaned more often. Thus it isalways desirable to minimize coagulation.

[0003] In EP-A 77038 describes the agglomeration of a dispersed rubberin the presence of a dispersion of an acid-group-containingagglomerating latex and in the presence of a neutral electrolyte. Sincethe agglomerating latex contains free acid groups, the agglomerationmust be carried out at a pH of higher than 7, in order to dissociate theacid. This process suffers from the drawback that, owing to the freeacid groups in the latex, the efficiency of the agglomeration isstrongly influenced by pH fluctuations. The pH must thus be tuned veryfinely in order to obtain reproducible results. This is feasible inlarge-scale production plants only at high expense. The chloridesproposed as neutral electrolytes suffer from the further drawback thatthey corrode the reaction vessels and pollute the wastewater, and evenresidues of these salts lead to corrosion problems during processing. Itwas also known from EP-A 517 539 that rubbers can be agglomerated withemulsion polymers containing at least 30% of units containing carboxylicacid groups. U.S. Pat. No. 3,049,501 discloses an agglomeration methodin which polyvinyl methyl ether containing acid groups is used at a pHfrom 8 to 11. GB-A 859 361 proposes an agglomerating latex free fromacid groups, together with an ammonium salt electrolyte.

[0004] The processes proposed in these publications do not adequatelyprevent the formation of coagulum. Moreover, the use of volatileelectrolytes may lead to problems such as foaming of the reactionmixture.

[0005] Agglomerating latices exhibiting no free acid groups and capableof causing agglomeration intrinsically, i.e., independently of whetherthe pH is above 7 during agglomeration or not, have been disclosed inH.-G. Keppler, H. Wesslau, J. Stabenow, Angew. Makromol. Chem. 2 (1968)pages 1 to 25.

[0006] It is an object of the invention to find a process by means ofwhich dispersed rubber particles can be efficiently agglomerated,especially in large-scale production, with the formation of coagulumminimized.

[0007] Accordingly we have found a process for the agglomeration of atleast one rubber (A), dispersed in an aqueous phase, by the addition ofa dispersion of at least one agglomerating polymer (B) in aqueous phase,in which an agglomerating polymer containing substantially no free acidgroups is used and in which the agglomeration is carried out in thepresence of at least one basic electrolyte. We have also found graftpolymers (C) obtainable from said agglomerated rubbers. We have alsofound thermoplastic molding compositions (D) which comprise said graftpolymers C and can be used for the preparation of shaped articles, filmsor fibers.

[0008] The rubbers A underlying the process of the invention can bemultifarious. For example silicone rubbers, olefin rubbers, such asethylene, propylene, ethylene/propylene, EPDM, diene, acrylate,ethylene-vinyl acetate rubbers or ethylene-butyl acrylate rubbers ormixtures of two or more of these rubbers can be used. Preferably,however, diene rubbers are used. Special preference is given as A todiene rubbers composed of

[0009] a1) from 50 to 100% by weight of at least one diene havingconjugated double bonds and

[0010] a2) from 0 to 50% by weight of one or more othermonoethylenically unsaturated monomers,

[0011] the sum of the percentages by weight being 100.

[0012] Suitable dienes having conjugated double bonds, a1), are, inparticular, butadiene, isoprene and the halogen-substituted derivativesthereof, e.g., chloroprene. Preference is given to butadiene orisoprene, particularly butadiene.

[0013] The other monoethylenically unsaturated monomers a2) which may bepresent in diene rubber A at the expense of monomers a1) may be, forexample:

[0014] vinylaromatic monomers such as styrene and styrene derivatives ofthe general formula

[0015] in which R¹ and R² independently stand for hydrogen or C₁-C₈alkyl;

[0016] acrylonitrile, methacrylonitrile;

[0017] C₁-C₄-alkyl esters of methacrylic acid or acrylic acid such asmethyl methacrylate, and also the glycidyl esters glycidyl acrylate andmethacrylate;

[0018] N-substituted maleimides such as N-methyl-, N-phenyl- andN-cyclohexylmaleimides;

[0019] acrylic acid, methacrylic acid, and dicarboxylic acids such asmaleic acid, fumaric acid and itaconic acid and also their acidanhydrides such as maleic anhydride;

[0020] nitrogen-functional monomers such as dimethylaminoethyl acrylate,diethylaminoethyl acrylate, vinylimidazole, vinylpyrrolidone,vinylcaprolactam, vinylcarbazole, vinylaniline, acrylamide andmethacrylamide;

[0021] aromatic and araliphatic esters of acrylic acid and methacrylicacid such as phenyl acrylate, phenyl methacrylate, benzyl acrylate,benzyl methacrylate, 2-phenylethyl acrylate, 2-phenylethyl methacrylate,2-phenoxyethyl acrylate and 2-phenoxyethyl methacrylate;

[0022] unsaturated ethers such as vinyl methyl ether,

[0023] and mixtures of these monomers.

[0024] Preferred monomers a2) are styrene, acrylonitrile, methylmethacrylate, glycidyl acrylate and methacrylate or butyl acrylate.

[0025] Generally, diene rubbers A exhibit a glass transition temperatureTg of less than 0° C. (determined as specified in DIN 53765).

[0026] The synthesis of rubbers A is known to the person skilled in theart or may be carried out by methods known to the person skilled in theart. Thus diene rubbers A can be prepared in a first step in which theyare not formed in a particulate state, for example via solutionpolymerization or gas-phase polymerization, and are then dispersed inthe aqueous phase in a second step (secondary emulsification).

[0027] Heterogenous, particle-forming polymerization processes arepreferred for the synthesis of rubbers A. Dispersion polymerization canbe carried out in known manner by, say, the emulsion, inverse emulsion,miniemulsion, microemulsion, or microsuspension polymerization method.

[0028] Dispersion polymerization can be carried out in an organicsolvent or an aqueous phase.

[0029] The rubbers A are preferably prepared in aqueous phase. Byaqueous phase is meant a solution, emulsion or suspension of thecorresponding monomers or polymers in water or in a solvent mixturecontaining a large proportion, i.e., at least 20% by weight, of water.

[0030] In one preferred embodiment, polymerization is carried out by theemulsion method, in which the monomers are polymerized in aqueousemulsion at from 20 to 100° C., preferably at from 50 to 80° C., inwhich case all components of the batch can be combined (batch process),or the monomer alone or an emulsion of monomer, water and emulsifierscan be gradually added to the other components (feed process).Furthermore, it is possible to carry out the reaction by a continuousmethod. Preference is given to the feed process.

[0031] Suitable emulsifiers are for example alkali metal salts of alkyl-or alkylaryl-sulfonic acids, alkyl sulfates, fatty alcohol sulfonates,salts of higher fatty acids containing from 10 to 30 carbons,sulfosuccinates, ether sulfonates or resin soaps. Preferably, use ismade of the alkali metal salts of alkylsulfonates or fatty acidscontaining from 10 to 18 carbons.

[0032] Their concentration is usually from 0.5 to 5% by weight, based onmonomers a) (sum of monomers a1 and a2).

[0033] Preferably, the preparation of the dispersion is carried outusing sufficient water to give the final dispersion a solids content offrom 20 to 50% by weight.

[0034] Free-radical initiators suitable for starting the polymerizationreaction are all those which decompose at the reaction temperaturechosen, i.e. both those which undergo decomposition thermally and thosewhich do so in the presence of a redox system. Suitable polymerizationinitiators are preferably free-radical initiators, for example peroxidessuch as preferably peroxodisulfates (e.g. sodium or potassiumpersulfate) or azo compounds such as azodiisobutyronitrile. However,redox systems, particularly those based on hydroperoxides such as cumenehydroperoxide, may alternatively be used.

[0035] Usually the polymerization initiators are used in a concentrationof from 0.1 to 2% by weight, based on monomers a).

[0036] The free-radical initiators and the emulsifiers are for exampleplaced in the reaction vessel as a single batch at the start of thereaction in batchwise mode, or are divided into a number of portionswhich are added batchwise at the start and at one or more intervalsthereafter, or are added continuously over a specific period. Thiscontinuous addition may follow a gradient, which may, for example, beascending or descending, linear or exponential, or stepped (stepfunction).

[0037] Use may also be made of molecular weight regulators such asethylhexyl thioglycolate, n- or tert-dodecyl mercaptan or othermercaptans, terpinols and dimeric α-methylstyrene or other compoundssuitable for molecular weight regulation. The molecular weightregulators are added to the reaction batch batchwise or continuously asdescribed above with reference to the free-radical initiators andemulsifiers.

[0038] The pH at which polymerization is carried out is influenced bythe type of emulsifiers used. Polymerization is generally carried out ata pH of preferably from 6 to 10. Buffering agents such asNa₂HPO₄/NaH₂PO₄, sodium pyrophosphate, sodium hydrogencarbonate orbuffers based on citric acid/citrate may also be used. Regulators andbuffering agents are used in conventional amounts, so that more detailedinformation thereon is unnecessary here.

[0039] The diene rubbers preferably used as A may, in a specialembodiment, be produced by polymerization of monomers a) in the presenceof a finely divided latex (“seed latex method” of polymerization). Thislatex is used as the initial batch and can consist of monomers capableof forming rubber-elastic polymers, or alternatively of other monomerssuch as those mentioned above. Suitable seed latices consist for exampleof polybutadiene or polystyrene.

[0040] In one preferred embodiment of the emulsion polymerization thediene rubbers A can be produced by the feed process. In this process aspecific fraction of monomers a) is used as initial batch andpolymerization is initiated, after which the remainder of the monomersa) (feed fraction) is added as a feed stream during polymerization. Thefeed parameters (gradient shape, rate, duration, etc.) are governed bythe other polymerization conditions. The same applies here, by analogy,as stated above with reference to the manner of adding free-radicalinitiator or emulsifier. In said feed process the fraction of monomersa) used as initial batch is preferably from 5 to 50% by weight and morepreferably from 8 to 40% by weight based on a). Preferably, the feedfraction of a) is fed in over a period of from 1 to 18 hours, morepreferably from 2 to 16 hours and most preferably from 4 to 12 hours.

[0041] Inverse emulsion polymerization differs from emulsionpolymerization in that instead of hydrophobic monomers dispersed in anaqueous phase, use is made of hydrophilic monomers dispersed in asubstantially nonaqueous phase.

[0042] Miniemulsion polymerization differs from emulsion polymerizationprimarily in that the mixture of monomers, water, emulsifiers andco-emulsifiers is subjected, in a first step, to high shearing forcesand the polymerization reaction is carried out in a second step. Thisproduces very fine monomer droplets. The batch is then polymerized bymeans of a water-soluble initiator, e.g., a persulfate. The particlesize distribution of the monomer droplets usually substantiallycorresponds to the later particle size distribution of the polymerparticles. The high shearing forces can be produced for example byultrasound or a microfluidizer appliance, or alternatively byhomogenizers. Details of the miniemulsion polymerization process may befound by the person skilled in the art in, say, P. Lovell, M. El-Aasser,Emulsion Polymerization and Emulsion Polymers, John Wiley, New York,1997, pp. 699-722.

[0043] In microemulsion polymerization very large amounts of emulsifierare used, thereby distinguishing it from emulsion polymerization. Inthis way similarly large monomer droplets are produced as inminiemulsion polymerization, but in the case of microemulsionpolymerization the droplets are thermodynamically stable.

[0044] In other respects the above statements concerning normal emulsionpolymerization apply to both miniemulsion and microemulsionpolymerization.

[0045] In microsuspension polymerization, a finely divided monomeremulsion is generally produced in a first step by the action of highshearing forces. For this purpose use is made of homogenizers, which arewell known to the person skilled in the art. But compared withminiemulsion polymerization, the droplets obtained are larger. Further,there are used, in microsuspension polymerization, at least oneemulsifier and at least one protective colloid.

[0046] The protective colloids suitable for stabilization of thedispersion during polymerization by the microsuspension polymerizationprocess are water-soluble polymers, for example cellulose derivativessuch as carboxymethyl cellulose and hydroxymethyl cellulose,poly(N-vinylpyrrolidone), poly(vinyl alcohol) and poly(ethylene oxide),anionic polymers such as polyacrylic acid and their copolymers, andcationic polymers such as poly(N-vinylimidazole). The concentration ofthese protective colloids is preferably from 0.1 to 10% by weight, basedon the total mass of the dispersion.

[0047] Preference is given to the use of one or more polyvinyl alcoholsas protective colloids, particularly those having a degree of hydrolysisbelow 96 mol %, preferably from 60 to 94 and more preferably from 65 to92 mol %. The preferred polyvinyl alcohols have a dynamic viscosity offrom 2 to 100 mPas, preferably from 4 to 60 mPas, measured on a 4% byweight strength solution in water at 20° C. according to DIN 53015.

[0048] The microsuspension polymerization is initiated using afree-radical polymerization initiator. Such compounds are known to theperson skilled in the art. In particular, the initiators used areorganic peroxides such as dilauryl peroxide or azo compounds such as2,2′-azobis(2-methylbutyronitrile) or 2,2′-azobis(isobutyronitrile).Also used as free-radical polymerization initiators are monomers whichspontaneously polymerize at elevated temperature.

[0049] The concentration of the initiator is usually from 0.05 to 4% byweight, based on the monomers.

[0050] Further additives such as buffering agents and molecular weightregulators can be added continuously or batchwise at the start of and/orduring the preparation of the monomer dispersion and/or duringpolymerization.

[0051] The monomer dispersion is usually prepared at room temperature,but higher or lower temperatures may be sensible depending on the typeof monomers and protective colloids used.

[0052] Preparation of the monomer dispersion may be effected batchwiseor continuously. Alternatively, it is possible to disperse thecomponents in a first step as a batch and then to subject the resultingdispersion to a second dispersing operation carried out continuously.

[0053] Polymerization is carried out in conventional manner, for exampleby heating the reactor contents, by which means the polymerizationreaction is initiated, or, in the case of a redox initiator, by bringingthe initiator into contact with the reducing agent. The polymerizationtemperature is governed, inter alia, by the monomers and initiatorsused, and also by the desired degree of crosslinking of the resultingpolymers A). Generally, polymerization is carried out at from 30 to 120°C., and if desired various temperatures can be used successively, or atemperature gradient can be employed.

[0054] The polymerization reaction is usually carried out with slow orgentle agitation, during which (unlike in the case of the precedingemulsification involving high shearing forces) the droplets are notbroken up further.

[0055] The particle size can thus be controlled, as already mentionedabove with respect to the miniemulsion and microsuspensionpolymerization methods, substantially by appropriately selecting andregulating the conditions used during preparation of the dispersion(e.g., choice of homogenizer, duration of homogenization, proportions ofmonomers to water to protective colloids, method of dispersion used(once, twice or more times, as a batch or continuously, with or withoutrecirculation), speed of rotation of the homogenizer, etc.).

[0056] The precise polymerization conditions, particularly as regardsthe type, amount and metering of the emulsifier and other polymerizationauxiliaries, are preferably selected such that the resulting particlesof rubbers A obtained by emulsion polymerization have a mean particlesize (weight-average particle size d₅₀) usually from 50 to 500 andpreferably from 70 to 300 and more preferably from 80 to 140 nm. Therubbers A obtained by miniemulsion polymerization usually have particlesizes of from 50 to 500 nm (weight-average particle size d₅₀).Microemulsion polymerization produces particle sizes (weight-averageparticle sizes d₅₀) in the range of from 20 to 80 nm. The particle sizesstated always refer to the d₅₀ value (weight average, determined byanalytical ultracentrifuge measurements as described by W. Mächtle, S.Harding (Eds.), AUC in Biochemistry and Polymer Science, Cambridge,Royal Society of Chemistry UK 1992 pp. 1447-1475).

[0057] The method of microsuspension polymerization generally producesparticles having a size (weight-average particle size d₅₀) in the rangeof from 0.3 to 10 μm. The particle sizes can be determined by the methodof Fraunhofer diffraction (H. G. Barth, Modern Methods of Particle SizeAnalysis, Wiley, NY 1984).

[0058] The monomers a) are polymerized conventionally up to a conversionof usually at least 90% and preferably greater than 95%, based on themonomers used.

[0059] The rubber A dispersed in the aqueous phase is then agglomeratedaccording to the invention. There may be more than one, for example twoor more, rubbers present in the dispersion. This can be achieved e.g.,by mixing dispersions of different rubbers. Agglomeration is achieved bythe addition of a dispersion of the agglomerating polymer B and thebasic electrolyte.

[0060] In the present invention, B contains substantially no free acidgroups, i.e., B contains, if at all, only free acid groups which mighthave come about through impurities or side reactions during manufactureof B. Examples of suitable agglomerating polymers are copolymerscontaining polar comonomers. Suitable agglomerating polymers includecopolymers of C₁-C₁₂ alkyl acrylates or C₁-C₁₂ alkyl methacrylates andpolar comonomers such as acrylamide, methacrylamide, ethacrylamide,n-butylacrylamide or maleamide.

[0061] It is preferred to use copolymers of

[0062] b1) from 80 to 99.9% by weight of (C₁-C₄-alkyl) esters of acrylicacid and

[0063] b2) from 0.1 to 20% by weight and preferably from 0.1 to 10% byweight of acrylamides,

[0064] the sum of monomers b1) and b2) being 100% by weight. Themonomers b1) used may be mixtures of various acrylates. Monomer b1) ispreferably ethyl acrylate. Preferred monomers b2) include acrylamide,methacrylamide, N-methylolmethacrylamide or N-vinylpyrrolidone ormixtures of said compounds. B is very preferably a copolymer of from 92to 99% by weight of ethyl acrylate and from 1 to 8% by weight ofmethacrylamide. Preferred agglomerating polymers B include those havinga molecular weight (weight average M_(w)) of from 30,000 to 300,000g/mol.

[0065] The concentration of the agglomerating polymers in the dispersionused for agglomeration should generally be in the range from 3 to 60% byweight and preferably from 5 to 40% by weight. The agglomeratingdispersion may, if desired, comprise a mixture of, say, two or moredifferent agglomerating polymers. Preferably B is dispersed in anaqueous phase.

[0066] Agglomeration is usually carried out using from 0.1 to 5 andpreferably from 0.5 to 3 parts by weight of the agglomerating dispersionper 100 parts by weight of the rubber, each based on solids.

[0067] The agglomeration is preferably carried out at a temperature offrom 20 to 120° C. and more preferably from 30 to 100° C. The additionof B can take place all at once or in portions, continuously oraccording to a feed profile over a certain period of time. In apreferred embodiment, the addition of B is carried out in such a mannerthat 1/1 to 1/100 of the total amount of B are introduced per minute.The agglomerating time is preferably from 1 minute to several hours, forexample up to two hours, and more preferably from 10 to 60 minutes.

[0068] In accordance with the invention, suitable basic electrolytesinclude organic or inorganic hydroxides. Inorganic hydroxides areespecially suitable. Monovalent basic electrolytes are preferred.Particular preference is given to the use of lithium hydroxide, sodiumhydroxide or potassium hydroxide. In one preferred embodiment, KOH isused as basic electrolyte. In another preferred embodiment, NaOH is usedas basic electrolyte. Additionally, however, mixtures of two or morebasic electrolytes can be used. This can be advantageous, for example,when it is desired to exert precise control over the growth of therubber particles. Thus it can be advantageous, for example, to usemixtures of LiOH with KOH or mixtures of LiOH with NaOH. Using mixturesof KOH and NaOH is a further option and a further preferred embodiment.

[0069] Generally, the electrolytes are dissolved prior to being added.The preferred solvent is the aqueous phase. Preference is given to theuse of dilute solutions, e.g., solutions with a concentration in therange from 0.001 to 0.1, particularly in the range from 0.001 to 0.05,more preferably less than 0.03, e.g., less than 0.025 g, of basicelectrolyte per mL of solvent. The addition of the basic electrolytescan take place prior to the addition of the agglomerating polymer,simultaneously therewith or separately or following the addition of B.An alternative possibility is to premix the basic electrolytes in thedispersion of B. In a preferred embodiment, the addition of the basicelectrolytes is carried out prior to the addition of the agglomeratingpolymer. Usually the basic electrolyte is used in an amount ranging from0.01 to 4, preferably from 0.05 to 2.5, particularly from 0.1 to 1.5% byweight, based on rubber A (as solids).

[0070] The pH during agglomeration is generally from 6 to 13. In apreferred embodiment it is from 8 to 13.

[0071] The agglomerated rubbers A produced by the process of theinvention are suitable for use as graft base for the synthesis of graftpolymers (C). Theoretically, the rubbers can be grafted with a very widevariety of unsaturated compounds. Appropriate compounds and methods areknown to the person skilled in the art. Preference is given to graftpolymers C which contain (based on C and solids)

[0072] c1) from 30 to 95, preferably from 40 to 90 and more preferablyfrom 40 to 85% by weight of graft base and

[0073] c2) from 5 to 70, preferably from 10 to 60, and more preferablyfrom 15 to 60% by weight of a graft component.

[0074] Preference is given to a graft component c2) comprising

[0075] c21)from 50 to 100, preferably from 60 to 100 and more preferablyfrom 65 to 100% by weight of a styrene compound of the general formula

[0076] in which R¹ and R² independently stand for hydrogen orC₁-C₈-alkyl,

[0077] c22) from 0 to 40%, preferably from 0 to 38% and more preferablyfrom 0 to 35% by weight of acrylonitrile or methacrylonitrile or amixture thereof,

[0078] c23) from 0 to 40, preferably from 0 to 30 and more preferablyfrom 0 to 20% by weight of one or more further monoethylenicallyunsaturated monomers.

[0079] The graft component c2) can be produced in one or more processsteps. The monomers c21), c22) and c23) may be added individually orintermixed. The ratio of the monomers in the mixture may be constant intime or follow a gradient. Alternatively, combinations of these methodscan be used.

[0080] For example, first of all styrene alone and then a mixture ofstyrene and acrylonitrile can be polymerized onto graft base c1).

[0081] If desired, however, other monomers c2) can be used, for examplemethyl methacrylate. Furthermore, component c2) may contain, at theexpense of monomers c21) and c22), one or more other monoethylenicallyunsaturated monomers c23). As regards monomers c23), reference is madeto the remarks concerning component a13).

[0082] Preferred graft components c2) are for example polystyrene andcopolymers of styrene and/or a-methylstyrene with one or more of theother monomers described under c22) and c23). Preference is given tomethyl methacrylate, N-phenylmaleimide, maleic anhydride andacrylonitrile and more preferably to methyl methacrylate andacrylonitrile.

[0083] As examples of preferred graft components c2) there may bementioned:

[0084] c2-1: polystyrene

[0085] c2-2: copolymer of styrene and acrylonitrile,

[0086] c2-3: copolymer of α-methylstyrene and acrylonitrile,

[0087] c2-4: copolymers of styrene and methyl methacrylate.

[0088] The amount of styrene or α-methylstyrene, or the total amount ofstyrene and α-methylstyrene, is very preferably at least 40% by weight,based on c2).

[0089] The graft polymers can be used for the preparation ofthermoplastic molding compositions and are for this purpose mixed withone or more other polymers. In this case the graft component c2) acts ascompatibility promoter between graft base c1) and the matrix polymerinto which the graft polymers C are embedded. Preferably, therefore,monomers c2) are the same as those of the matrix. If the matrix consistsentirely or predominantly of a poly(styrene-co-acrylonitrile) (SAN), thegraft component as well will usually entirely or predominantly consistof styrene and/or α-methylstyrene and acrylonitrile.

[0090] Graft component c2) is generally polymerized in emulsion in thepresence of the agglomerated rubber A. The process is usually carriedout at from 20 to 100° C. and preferably from 50 to 80° C. In a mannersimilar to that described above regarding the preparation of the rubber,grafting can take place as a batch process, a feed process or acontinuous process.

[0091] The polymerization initiator used for the graft component cancomprise the same water-soluble compounds as employed duringpolymerization of the graft base. In the same way use can be made ofoil-soluble initiators or initiators that are soluble in the monomer,examples being dialkyl peroxides such as dilauryl peroxide and dibenzylperoxide, per esters such as tert-butyl perpivalate and tert-butylperoxyneodecanoate, further diperoxyketals, peroxycarbonates and azocompounds such as azodiisobutyronitrile (azobisisobutyronitrile, AIBN)and azodiisovaleronitrile (ADVN). Furthermore, hydroperoxides,particularly cumene hydroperoxide, are suitable as polymerizationinitiators.

[0092] Details on how to carry out the grafting reaction in emulsion maybe found, for example, in DE-A 24 27 960 and EP-A 62901.

[0093] The gross composition of the graft polymers C is not affected bythe stated embodiments of the process.

[0094] Also suitable are graft polymers having a number of “soft” and“hard” stages, e.g., having the structure c1)-c2)-c1)-c2) orc2)-c1)-c2), particularly in the case of larger particles.

[0095] If grafting is accompanied by the formation of ungrafted polymersof the monomers c2), these amounts, which are usually below 10% byweight of c2), are assigned to the mass of component C.

[0096] Graft copolymers C are, for the preparation of thermoplasticmolding compositions (D), preferably blended with at least one matrixpolymer and optionally other components. These are described below.

[0097] Examples of suitable matrix polymers d1) are amorphous polymers.

[0098] Examples thereof are SAN (styrene/acrylonitrile), AMSAN(α-methylstyrene/acrylonitrile), styrene/maleimide, SMSAN(styrene/maleic acid (anhydride)/acrylonitrile polymers or SMA(styrene/maleic anhydride).

[0099] Preferably, component d1) is a copolymer of

[0100] d11) from 60 to 100% by weight and preferably from 65 to 80% byweight of units of a vinylaromatic monomer, preferably styrene, asubstituted styrene or a (meth)acrylate or a mixture thereof,particularly of styrene and/or α-methylstyrene,

[0101] d12)from 0 to 40% by weight and preferably from 20 to 35% byweight of units of an ethylenically unsaturated monomer, preferablyacrylonitrile or methacrylonitrile or methyl methacrylate (MMA),particularly acrylonitrile.

[0102] According to one embodiment of the invention it is composed of60-99% by weight of vinylaromatic monomers and 1-40% by weight of atleast one of the other monomers stated.

[0103] In one embodiment of the invention the component d1) used is acopolymer of styrene and/or α-methylstyrene with acrylonitrile. Theacrylonitrile content in these copolymers is 0-40% by weight andpreferably 20-35% by weight, based on the total weight of d1).

[0104] The thermoplastic molding compositions D can, furthermore,contain, as matrix polymer, in addition to d1) or alone, preferably atleast one polymer selected from the group consisting of partiallycrystalline polyamides, partially aromatic polyamides, polyesters,polyoxyalkylenes, polycarbonates, polyarylene sulfides and polyetherketones. Alternatively, mixtures of two or more of said polymers can beused. Of course, it is possible to use mixtures of different individualpolymers, e.g., mixtures of different polyamides, different polyestersor different polycarbonates, as matrix polymers.

[0105] Suitable polymers d2) in the molding composition of the inventionare partially crystalline, preferably linear, polyamides such aspolyamide-6, polyamide-6,6, polyamide-4,6, polyamide-6,12 and partiallycrystalline copolyamides (d3) based on these components. Furthermore,partially crystalline polyamides can be used whose acid componentconsists completely or partially of adipic acid and/or terephthalic acidand/or isophthalic acid and/or suberic acid and/or sebacic acid and/orazelaic acid and/or dodecanedicarboxylic acid and/or acyclohexanedicarboxylic acid, and whose diamine component consistscompletely or partially of, in particular, m- and/or p-xylylenediamineand/or hexamethylenediamine and/or 2,2,4- and/or2,4,4-trimethylhexamethylenediamine and/or isophronediamine, and thecomposition of which is basically known from the prior art.

[0106] Additionally, the polymers d4) used can be polyesters, preferablyaromatic-aliphatic polyesters. Examples are polyalkylene terephthalates,based, for example, on ethylene glycol, 1,3-propanediol, 1,4-butanediol,1,6-hexanediol and 1,4-bishydroxymethylcyclohexane, and alsopolyalkylene naphthalates.

[0107] Furthermore, polymers d5) used can be polyoxyalkylenes, e.g.,polyoxymethylene.

[0108] Suitable polycarbonates d6) are known per se or can be obtainedby known methods. Preference is given to polycarbonates based ondiphenyl carbonate and bisphenols. The preferred bisphenol is2,2-di(4-hydroxyphenyl)propane, generally referred to, as below, asbisphenol A.

[0109] Instead of bisphenol A use can be made of other aromaticdihydroxy compounds, particularly 2,2-di(4-hydroxyphenyl)pentane,2,6-dihydroxynaphthalene, 4,4′-dihydroxydiphenyl sulfone,4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxydiphenyl sulfide,4,4′-dihydroxydiphenylmethane, 1,1-di(4-hydroxyphenyl)ethane,4,4-dihydroxybiphenyl or dihydroxydiphenylcycloalkanes, preferablydihydroxydiphenylcyclohexanes or dihydroxylcyclopentanes, particularly1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane and also mixtures ofthe aforementioned dihydroxy compounds.

[0110] Particularly preferred polycarbonates are those based onbisphenol A or bisphenol A together with up to 80 mol % of theaforementioned aromatic dihydroxy compounds.

[0111] Alternatively, copolycarbonates can be used; of particularinterest are copolycarbonates based on bisphenol A anddi(3,5-dimethyldihydroxyphenyl) sulfone, which are characterized by highheat distortion resistance.

[0112] Also suitable are polyarylene sulfides, particularlypolyphenylene sulfide.

[0113] Furthermore, molding compositions D can contain, as a furthercomponent, additives E.

[0114] Preferred thermoplastic molding compositions contain, ascomponent E, 0-50% by weight, preferably 0-40% by weight and morepreferably 0-30% by weight of fibrous or particulate fillers or mixturesthereof, based, in each case, on the total molding composition.

[0115] If used, reinforcing agents such as carbon fibers and glassfibers are usually employed in amounts of 5-50% by weight based on thetotal molding composition.

[0116] The glass fibers used can be of glass type E, A or C and arepreferably coated with size and adhesion promoter. Their diameter isgenerally from 6 to 20 μm. It is possible to use rovings or choppedstrands (staple fibers) having a length of 1-10 μm and preferably 3-6μm.

[0117] Furthermore, fillers or reinforcing materials, such as glassbeads, mineral fibers, whiskers, aluminum oxide fibers, mica, quartzpowder and wollastonite, can be added.

[0118] In addition, metal flakes, e.g., aluminum flakes, metal powders,metal fibers, metal-coated fillers, e.g., nickel-coated glass fibers,and other additives capable of shielding against electromagnetic wavesmay be blended into molding compositions D. Furthermore, the moldingcompositions can be mixed with additional carbon fibers, carbon black,in particular conductive carbon black, or nickel-coated C fibers.

[0119] Molding compositions D can contain other additives as well. Asexamples thereof there may be mentioned: dyes, pigments, colorants,antistatic agents, antioxidants, stabilizing agents for improvingthermostability, increasing light stability, improving resistance tohydrolysis and resistance to chemicals, agents counteracting thermaldecomposition and, in particular, lubricants or release agents, whichare advantageous when manufacturing shaped articles or moldings orfilms. Metering of these further additives can take place at any stageof the process for the manufacture of D, but preferably early on, inorder to exploit the stabilizing action (or other specific effects) ofthe respective additive at an early stage.

[0120] Suitable stabilizers are for example hindered phenols, but alsovitamin E or compounds having an analogous structure, and butylatedcondensation products of p-cresol and dicyclopentadiene and also HALSstabilizers (Hindered Amine Light Stabilizers), benzophenones,resorcinols, salicylates and benzotriazoles. Other suitable compoundsare e.g., thiocarboxylates. Preference is given to C₆-C₂₀ fatty acidesters of thiopropionic acid, stearyl and lauryl esters beingparticularly preferred. Very special reference is given to the use ofdilauryl thiodipropionate, distearyl thiodipropionate or mixturesthereof. Further additives are for example HALS absorbers, such asbis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, or UV absorbers such as2H-benzotriazol-2-yl-4-methylphenol. Such additives are usually employedin amounts of up to 2% by weight (based on the total mixture).

[0121] Suitable lubricants and mold release agents are stearic acids,stearyl alcohol, stearates, amide waxes (bis-stearylamide), polyolefinwaxes or, generally, higher fatty acids, derivatives thereof andmixtures of such fatty acids containing from 12 to 30 carbons. Theamounts of these additives are in the range from 0.05 to 5% by weight.

[0122] In addition, silicone oils, oligomeric isobutylene or similarmaterials are suitable for use as additives. If used, the usualconcentrations thereof are from 0.001 to 5% by weight. Pigments, dyes,color brighteners, such as ultramarine blue, phthalocyanines,titanium(IV) oxide, cadmium sulfides, derivatives ofperylenetetracarboxylic acid are also useful.

[0123] Processing assistants and stabilizers such as UV stabilizers,lubricants and antistatic agents, if used, are usually employed inamounts of from 0.01 to 5% by weight, based on the total moldingcomposition.

[0124] Mixing of graft polymers C with the other constituents to producemolding compositions D may be carried out by any known method and in anydesired manner. However, blending of the components is preferablycarried out by coextruding, kneading or roll-milling the components attemperatures of, say, from 180 to 400° C., the components having beenpreviously isolated if necessary from the solution or aqueous dispersionobtained in the polymerization. The products of the graftcopolymerization (component C), obtained in aqueous dispersion, can forexample be only partially dewatered and mixed as moist crumbs with thematrix polymers, in which case drying of the graft copolymers iscompleted during the mixing operation.

[0125] The molding compositions can be processed to shaped articles,films or fibers.

[0126] According to one embodiment of the invention, these can beprepared from molding compositions D by known methods of processingthermoplastics. In particular, production may be effected bythermoforming, extruding, injection molding, calendering, blow molding,pressing, pressure sintering, deep drawing or sintering, preferably byinjection molding.

[0127] The molded articles prepared from molding compositions D arecharacterized by relatively high impact strengths. In addition, theyhave an improved surface quality, particularly greater luster.

[0128] The invention is illustrated below with reference to thefollowing examples.

EXAMPLES Test Methods

[0129] Charpy Impact Strength (ak [kJ/m²]):

[0130] Tests were carried out on specimens (80×10×4 mm, preparedaccording to ISO 294 in a family mold at a mass temperature of 240° C.and a mold temperature of 50° C.) at 23° C. and −40° C. according to ISO179-2/leA (F).

[0131] Puncture Resistance (Multiaxial Toughness) [Nm]:

[0132] Tests were carried out according to ISO 6603-2 on plates (60×60×2mm, prepared according to ISO 294 in a family mold at a mass temperatureof 240° C. and a mold temperature of 50° C.)

[0133] Flowability (MVR [ml/10′]):

[0134] Tests were carried out according to ISO 1133 B on the polymermelt at 220° C. under a load of 10 kg

[0135] Elasticity (Modulus of Elasticity [MPa]):

[0136] Tests were carried out according to ISO 527-2/1A/50 on specimens(prepared according to ISO 294 at a mass temperature of 250° C. and amold temperature of 60° C.)

[0137] Amount of Coagulum:

[0138] The amount of coagulum relative to the graft rubber is determinedafter filtration through a sieve having a mesh size of about 1 mm, driedat 80° C. under nitrogen (200 mbar) for 17 hours.

[0139] Particle Size:

[0140] The mean particle size d stated is the weight average of theparticle size, as determined with an analytical ultracentrifugefollowing the method of W. Mächtle, S. Harding (Eds.), AUC inBiochemistry and Polymer Science, Royal Society of Chemistry Cambridge,UK 1992 pp. 1447-1475. The ultracentrifuge readings give the integralmass distribution of the particle diameter in a sample. This makes itpossible to determine what percentage by weight of the particles have adiameter equal to or smaller than a specific size.

[0141] The weight-average particle diameter d₅₀ indicates that particlediameter at which 50% by weight of all particles have a larger particlediameter and 50% by weight have a smaller particle diameter.

[0142] Swell Index and Gel Content [%]

[0143] A film was prepared from the aqueous dispersion of the graft baseby evaporating the water. To 0.2 g of this film there were added 50 g oftoluene. After a period of 24 hours the toluene was removed from theswollen sample by filtration with suction and the sample was weighed.After drying in vacuo at 110° C. over a period of 16 hours, the samplewas reweighed. The indicators were calculated as follows:$\begin{matrix}{{{Swell}\quad {index}\quad {SI}} = \frac{{{mass}\quad {of}\quad {swollen}},{{suction}\text{-}{filtered}\quad {specimen}}}{{mass}\quad {of}\quad {vacuum}\text{-}{dried}\quad {specimen}}} \\{{{Gel}\quad {content}} = {{\frac{{mass}\quad {of}\quad {vacuum}\text{-}{dried}\quad {specimen}}{{initial}\quad {mass}\quad {of}\quad {unswollen}\quad {specimen}} \cdot 100}\quad \%}}\end{matrix}$

[0144] Butadiene Rubber (A₁ to A₅)

[0145] Synthesis of the butadiene rubber (A₁ to A₅) took place byemulsion polymerization by the feed process. As comonomer 10% by weightof styrene were used.

[0146] The butadiene rubbers had the following properties: Rubber Swellindex Gel content [%] d₅₀ [nm] A₁ 19 77 109 A₂ 28 74 100 A₃ 17 86 116 A₄22 76 104 A₅ 28 72 106

Experiment a (For Comparison)

[0147] To 60.47 kg of a dispersion of A₁ in water (solids content 43% byweight) there were added, at 55° C., 6.5 kg of a dispersion of copolymerB₁ (solids content 10% by weight, composition of B₁: 95.5% of ethylacrylate and 4.5% of methacrylamide (MAM)).

[0148] To the resulting dispersion of the agglomerated rubber A₁ anemulsifier was added. There were then added 0.98 kg of acrylonitrile(AN), 2.52 kg of styrene (S) and tert-dodecyl mercaptan (regulator). Theinitiator system used was one based on cumene hydroperoxide and dextroseand polymerization was carried out at a temperature in the range fromabout 60 to about 70° C. There were then added a further 2.94 kg ofacrylonitrile, 7.56 kg of styrene and regulator, emulsifier andinitiator. On completion of the polymerization reaction 0.05% ofsilicone oil and 0.6% of a stabilizer mixture, based, in each case, onthe total solids, were added and the mixture was allowed to cool down.

[0149] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C_(V1) was isolated and processedwith poly(styrene-co-acrylonitrile) (SAN) having an acrylonitrilecontent of 24% by weight, by extrusion, to form a molding compositionD_(V1) having a content of 29% by weight of C_(V1).

Experiment b (Invention)

[0150] Experiment a was repeated except that 0.27% by weight of KOH,based on the solids content of the dispersion of A₂, was added to thedispersion of the rubber prior to the addition of copolymer B₁.

[0151] The resulting dispersion was precipitated by means of magnesiumsulfate solution. The resulting graft rubber C₁ was isolated andprocessed with SAN having an acrylonitrile content of 24% by weight, byextrusion, to form a molding composition D₁ having a content of 29% byweight of C₁.

Experiment c (Invention)

[0152] To 4727.3 g of the dispersion of A₃ in water (solids content 44%by weight there were added 11.2 g of a 10% by weight strength KOHsolution. The fraction of KOH solids was 0.054% by weight based on thesolids content of the dispersion of A₃. The mixture was then heated to55° C. A 10% by weight strength dispersion of copolymer B₁ was thenadded, the added amount of solids of this agglomerating dispersion being2.5% of the solids content of the polybutadiene dispersion.

[0153] 14.4 g of a 10% by weight strength KOH solution, emulsifier andwater were then added and stirring was continued for a few minutes.

[0154] 78.4 g of acrylonitrile, 201.6 g of styrene and tert-dodecylmercaptan were then added. The reaction mixture was heated and aninitiator system based on cumene hydroperoxide and dextrose was addedthereto, and the mixture was polymerized at about 70° C. A further 235.2g of acrylonitrile, 604.8 kg of styrene and regulator and alsoemulsifier, initiator and water and 3.84 g of a 10% by weight strengthsolution of KOH in water were then added. On completion of thepolymerization reaction 0.05% of silicone oil and 0.6% of a stabilizermixture, based, in each case, on the total solids content, were addedand the mixture was allowed to cool down.

[0155] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₂ was isolated and processed withSAN having an acrylonitrile content of 28% by weight, by extrusion, toform a molding composition D₂ having a content of 29% by weight of C₂.

Experiment d (Invention)

[0156] Experiment c was repeated except that 0.11% by weight of KOHbased on the solids content of the dispersion of A₃ was added to thedispersion of the rubber prior to addition of copolymer B₁.

[0157] The resulting dispersion was precipitated by means of magnesiumsulfate solution. The resulting graft rubber C₃ was isolated andprocessed with SAN having an acrylonitrile content of 28% by weight, byextrusion, to form a molding composition D₃ having a content of 29% byweight of C₃.

Experiment e (Invention)

[0158] Experiment c was repeated except that 0.27% by weight of KOH,based on the solids content of the dispersion of A₃, was added to thedispersion of the rubber prior to the addition of copolymer B₁.

[0159] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₄ was isolated and processed withSAN having an acrylonitrile content of 28% by weight, by extrusion, toform a molding composition D₄ having a content of 29% by weight of C₄.

Experiment f (For Comparison)

[0160] To 4952.4 g of a dispersion A₂ (solids content 42% by weight) inwater there was added, at about 70° C., a 10% by weight strengthagglomerating dispersion of B₂ (composition of B₂: 96% of ethyl acrylateand 4% of MAM), the added amount of solid material of the agglomeratingdispersion being 4% of the solids content of the polybutadienedispersion.

[0161] Following agglomeration, emulsifier and initiator (potassiumpersulfate) were added. 46.67 g of acrylonitrile, 140 g of styrene andregulator were then added. A mixture of 233.33 g of acrylonitrile, 700 gof styrene and regulator was then added over a period of 190 minutes,the temperature being raised to 77° C. after over half of the time. Oncompletion of the addition of monomer, initiator was again added and thepolymerization was continued.

[0162] To the dispersion there were added 0.02% by weight of siliconeoil and 0.2% by weight of a stabilizer, based, in each case, on thetotal solids content, and the mixture was cooled.

[0163] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C_(V2) was isolated and processedwith SAN having an acrylonitrile content of 24% by weight, by extrusion,to form a molding composition D_(V2) having a content of 29% by weightof C_(V2).

Experiment g (Invention)

[0164] Experiment f was repeated except that additionally 0.54% of KOH,based on the solids content of the polybutadiene dispersion, was added.

[0165] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₅ was isolated and processed withSAN having an acrylonitrile content of 24% by weight, by extrusion, toform an ABS molding composition D₅ having a content of 29% by weight ofC₅.

Experiment h (Invention)

[0166] Experiment f was repeated except that additionally 0.27% of KOH,based on the solids content of the polybutadiene dispersion, was added.The added amount of solid material in the agglomerating dispersion was2.5% of the solids content of the polybutadiene dispersion.

[0167] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₆ was isolated and processed withSAN having an acrylonitrile content of 24% by weight, by extrusion, toform a molding composition D₆ having a content of 29% by weight of C₆.

Experiment i (Invention)

[0168] Experiment f was repeated except that additionally 0.27% of KOH,based on the solids content of the polybutadiene dispersion, was added.The added amount of solid material in the agglomerating dispersion of B₃(composition of B₃: 94% of ethyl acrylate and 6% of MAM) was 2.5% of thesolids content of the polybutadiene dispersion.

[0169] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₇ was isolated and processed withSAN having an acrylonitrile content of 24% by weight, by extrusion, toform a molding composition D₇ having a content of 29% by weight of C₇.

Experiment j (Invention)

[0170] To 5580 g of a dispersion A₄ (solids content 40% by weight) inwater there was added, at about 70° C., 0.37% by weight strength KOH,based on the solids content of the dispersion of A₄. Then a 10% byweight strength agglomerating dispersion of B₂ (composition of B₂: 95.5%of ethyl acrylate and 4.5% of MAM), the added amount of solid materialof the agglomerating dispersion being 1.5% of the solids content of thepolybutadiene dispersion.

[0171] Following agglomeration, emulsifier and initiator (potassiumpersulfate) were added. 47.9 g of acrylonitrile and 180 g of styrenewere then added. A mixture of 239 g of acrylonitrile and 900 g ofstyrene was then added over a period of 190 minutes, the temperaturebeing raised to 77° C. after over half of the time. On completion of theaddition of monomer, initiator was again added and the polymerizationwas continued.

[0172] To the dispersion there was added 0.2% by weight of a stabilizer,based on the total solids content, and the mixture was cooled.

[0173] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₈ was isolated and processed withSAN having an acrylonitrile content of 24% by weight, by extrusion, toform a molding composition D₈ having a content of 29% by weight of C₈.

Experiment k (Invention and For Comparison)

[0174] Experiment j was repeated except that additionally the type andamount of electrolyte indicated in Table 4, based on the solids contentof the polybutadiene dispersion, were added.

[0175] The dispersion was precipitated by means of magnesium sulfatesolution. The resulting graft rubber C₉ to C₁₁ and C_(v3) to C_(v7) wasisolated and processed with SAN having an acrylonitrile content of 24%by weight, by extrusion, to form an ABS molding composition D₉ to D₁₁and D_(v3) to D_(v7) having a content of 29% by weight of C₉ to C₁₁ andC_(v3) to C_(v7), respectively

Experiment l (Invention and For Comparison)

[0176] The procedure of experiment j was repeated. The rubber used wasthe rubber A₅.

[0177] The agglomerating polymer used was the copolymer B₁. Forcomparison, the copolymers B_(v1) to B_(v4) were used, containingacrylic acid or methacrylic acid groups and being prepared as follows:

[0178] Preparation of B₁

[0179] 333 g of ethyl acrylate, water, emulsifier and potassiumpersulfate were introduced as an initial charge, adjusted to a pH offrom 8 to 9, and stirred at 80° C. Then a further 2681 g of ethylacrylate, 126 g of meth acrylamide, emulsifier, water and free-radicalinitiator were metered in. After about 4½ hours, the reaction mixturewas cooled to room temperature and the resulting dispersion was dilutedin water to 10% by weight.

[0180] Preparation of B_(v1)

[0181] The procedure described under B₁ was repeated but initiallyintroducing 360 g of ethyl acrylate and metering in 2905 g of ethylacrylate and, instead of methyl acrylate, 136 g of acrylic acid.

[0182] After the reaction mixture had been cooled to room temperature,the dispersion was diluted to 10% by weight with an aqueous KOH solutioncontaining an amount of KOH equimolar with the acrylic acid.

[0183] Preparation of B_(v2)

[0184] The procedure described under B_(v1) was repeated but usingmethacrylic acid instead of acrylic acid.

[0185] Preparation of B_(v3)

[0186] The procedure described under B_(v1) was repeated except that thedispersion was diluted to 10% by weight with water instead of aqueousKOH solution.

[0187] Preparation of B_(v4)

[0188] The procedure described under B_(v2) was repeated except that thedispersion was diluted to 10% by weight with water instead of aqueousKOH solution.

[0189] When using B_(v3) and B_(v4), an equimolar amount of KOH withrespect to acrylic acid or methacrylic acid, respectively, was added inaddition to the amount of KOH stated in Table 5.

[0190] The results of the experiments are compiled in Table 5. TABLE 1Comparison Invention Experiment a b Rubber A A₁ A₂ Ratio AN/S in C 28/72(C_(v1)) 28/72 (C₁) Conc. of MAM in B₁ [%] 4.5 4.5 Amount of B₁ [%] 2.52.5 Electrolyte none KOH Amount of electrolyte [%] 0.27 Initiator RedoxRedox pH (following grafting) 9.58 9.92 Particle size of C 238 369 d₅₀[nm] Conc. of AN in SAN [%] 24 24 ak (23° C.) [kJ/m²] 13.6 19.7 ak (−40°C.) [kJ/m²] 4 9.1 Puncture resistance [Nm] 23.6 21.2 MVR (220/10)[cm³/10 min] 16.4 17.7 E modulus [MPa] 2080 2040 Coagulum [%] 1.2 0.3

[0191] TABLE 2 Invention Invention Invention Experiment c d e Rubber AA₃ A₃ A₃ Ratio of AN/S in C 28/72 (C₂) 28/72 (C₃) 28/72 (C₄) Conc. ofMAM [%] in B 4.5 4.5 4.5 Amount of B [%] 2.5 2.5 2.5 Electrolyte KOH KOHKOH Amount of electrolyte [%] 0.054 0.11 0.27 Initiator Redox RedoxRedox pH (following grafting) 9.82 9.97 10.28 Particle size of C 151 267325 d₅₀ [nm] Conc. of AN in SAN [%] 28 28 28 ak (23° C.) [kJ/m²] 22.220.7 21.3 ak (−40° C.) [kJ/m²] 7.6 7.6 7.8 Puncture resistance [Nm] 27.825.9 26.4 MVR (220/10) [cm³/10 min] 20.5 19.5 18.7 E modulus [MPa] 22302210 2170 Coagulum [%] 0.15 0.15 0.075

[0192] TABLE 3 Compari- Inven- Inven- Inven- son tion tion tionExperiment f g h i Rubber A A₂ A₂ A₂ A₂ Ratio of AN/S in C 25/75 25/7525/75 25/75 (C_(v2)) (C₅) (C₆) (C₇) Conc.of MAM [%] in B 4 4 4 6 Amountof B [%] 4 4 2.5 2.5 Electrolyte none KOH KOH KOH Amount of electrolyte[%] 0.54 0.27 0.27 Initiator KPS KPS KPS KPS Particle size of C 207 350358 362 d₅₀ [nm] pH (following grafting) 8.87 10.58 10.23 10.10 Conc. ofAN in SAN [%] 24 24 24 24 ak (23° C.) [kJ/m²] 11.1 25,.3 25.2 19 ak(−40° C.) [kJ/m²] 5.8 7.5 8.3 7.3 Puncture resistance [Nm] 5.7 12.3 29.421.4 MVR (220/10) [cm³/10 min] 23.7 21.1 20.2 23.5 E modulus [MPa] 24052367 2278 2384 Coagulum [%] 0.06 0.08 0.02 0.06

[0193] TABLE 4 Invention Invention Comparison Comparison ComparisonInvention Invention Comparison Comparison Experiment j k k k k k k k kRubber A A₄ A₄ A₄ A₄ A₄ A₄ A₄ A₄ A₄ Ratio of AK/S in C 21/79 (C₈) 21/79(C₉) 21/79 (C_(v3)) 21/79 (C_(v4)) 21/79 (C_(v5)) 21/79 (C₁₀) 21/79(C₁₁) 21/79 (C_(v6)) 21/79 (C_(v7)) Conc. of MAM [%] in B 4.5 4.5 4.54.5 4.5 4.5 4.5 4.5 4.5 Amount [%] in B 1.5 1.5 1.5 1.5 1.5 2.5 2.5 2.52.5 Electrolyte KOH NaOH NaHCO₃ KCl K₂SO₄ KOH NaOH NaHCO₃ K₂SO₄ Amountof electrolyte 0.37 0.2638 0.5542 0.4906 0.5734 0.27 0.1925 0.40440.4193 [%] Initiator KPS KPS KPS KPS KPS KPS KPS KPS KPS pH (followinggrafting) 11.26 11.58 8.84 10.61 10.56 PSD of C 140 141 135 324 299 d₅₀[nm]  D50 [nm] Conc. of AN in SAN [%] 24 24 24 24 24 PB content (sec.)[%] 29.1 29.2 28.3 28.3 29.5 ak 23° C. [kJ/m²] 23.3 23 23.1 21.4 22.3 ak−40° C. [kJ/m²] 7.2 7.6 8.1 7.8 7.9 Puncture resistance 23 ° C. [Nm] MVR220/10 16.3 16.4 17.1 16.8 15.9 [ml/10 min] Vicat B50 [° C.] 98.3 98.398.5 98.4 98.2 Coagulum (t)  grams 3.6 12.35 137.4 0.8 0.8 Coagulum (%)0.11 0.39 4.29 fully fully 0.03 0.03 coagulated fully coagulatedcoagulated coagulated

[0194] TABLE 5 Inven- Com- Com- Com- Com- tion parison parison parisonparison Experiment l l l l l Rubber A A₅ A₅ A₅ A₅ A₅ Ratio of AN/S in C21/79 21/79 21/79 21/79 21/79 (C₁₂) (C_(V8)) (C_(V9)) (C_(V10))(C_(V11)) B B₁ B_(v1) B_(v2) B_(v3) B_(v4) Amount [%] in B 1.5 1.5 1.51.5 1.5 Electrolyte KOH KOH KOH KOH KOH Amount of electrolyte 0.27 0.270.27 0.27 0.27 [%] Initiator KPS KPS KPS KPS KPS pH (following grafting)10.94 11.4 10.93 10.77 10.86 PSD of C d₅₀ [nm]  D50 [nm] n.g. n.g. n.g.n.g. n.g. Conc. of AN in SAN [%] 24 24 24 24 24 PB content (sec.) [%]28.3 28.5 28.9 28.2 28.3 ak 23° C. [kJ/m²] 25.5 25.1 25.5 25.2 25.1 ak−40° C. [kJ/m^(2]) 5.5 5.5 5.6 5.3 5.4 Puncture resistance 19.3 13.918.3 18.2 16.0 23° C. [Nm] MVR 220/10 20.1 19.4 18.1 20.9 20.1 [ml/10min] Vicat B50 [° C.] 96.3 96.2 95.7 95.9 95.8 Coagulum (t)  grams 1.742.2 9.2 39.1 12.1 Coagulum (%) 0.05 1.32 0.29 1.22 0.38

1. A process for the agglomeration of at least one rubber (A), dispersedin an aqueous phase, by the addition of a dispersion of at least oneagglomerating polymer (B) in aqueous phase, wherein the agglomeratingpolymer B used is one containing substantially no free acid groups andthe agglomeration is carried out in the presence of at least one basicelectrolyte comprising an organic or inorganic hydroxide.
 2. A processas claimed in claim 1, wherein the agglomerating polymer B used is acopolymer of (based on B): b1) from 80 to 99.9% by weight of at leastone (C₁-C₄ alkyl)ester of acrylic acid and b2) from 0.1 to 20% by weightof acrylamide.
 3. A process as claimed in claim 1 or claim 2, whereinthe basic electrolyte used is KOH.
 4. A process as claimed in any ofclaims 1 to 3, wherein the rubber A used is a diene rubber of (based onA): a1) from 50 to 100% by weight of at least one diene havingconjugated double bonds and a2) from 0 to 50% by weight of one or moreother monoethylenically unsaturated monomers.
 5. A process as claimed inany of claims 1 to 4, wherein the basic electrolyte is used in an amountof from 0.01 to 1.5% by weight based on A.
 6. A method of using rubbersA agglomerated by the process as claimed in any of claims 1 to 5 for thepreparation of graft polymers (C).
 7. A graft polymer C containing(based on C): c1) from 30 to 95% by weight of rubber A agglomerated bythe process as claimed in any of claims 1 to 5 and c2) from 5 to 70% byweight of a graft base.
 8. A method of using a graft polymer C asclaimed in claim 7 for the preparation of a thermoplastic moldingcomposition (D).
 9. A thermoplastic molding composition D comprising agraft polymer C as claimed in claim
 7. 10. A method of using athermoplastic molding composition D as claimed in claim 9 for thepreparation of shaped articles films or fibers.